This invention relates to the use of colloids labeled with alpha emitting radionuclide for a therapeutic use. Therapeutic uses contemplated includes treatment of rheumatoid arthritis, other inflammation of the joints, and cancer. Particularly, alpha emitting radionuclides are advantageously used for cancer therapy because they deliver high LET*, are lethal in absence of oxygen, and only penetrate a few cell diameters. Conventional cancer therapy employs surgery, radiation and chemotherapy. Each of these methods suffers a serious drawback in that it is not highly selective between healthy and cancerous cells. In order to be effective, these previous therapies kill or remove large amounts of healthy tissue. Furthermore, chemotherapy adversely affects the immune system so that death or serious illness often arises from fungal, bacteria or viral infections. FNT * LINEAR ENERGY TRANSFER
The present therapy for rheumatoid arthritis includes aspirin, nonsteroidal anti-inflammatory agents, remission-inducing agents and intraarticular administration of corticosteroids. In some cases where medical therapy has been unsuccessful, surgical synovectomy has provided symptomatic relief for periods of from two to five years. Disadvantages of this later procedure, aside from the fact that the benefits are only temporary, are the risks of surgery and anesthesia, as well as the expense of prolonged hospitalization and intensive rehabilitation thereafter. Radiation synovectomy has been used extensively in Europe as an alternative to surgical synovectomy. Heretofore, it has been suggested that beta emitters be used for radiation synovectomy, but one of the problems is that the delivery systems for the radionuclide tend to leak out of the joint and thereafter deliver radiation to various parts of the body.
Alpha emitters are particularly advantageous, as heretofore stated because of the short range of the effect thereof which is advantageous not only in the treatment of cancer but also in the treatment of joints since previous work with radionuclide injected in the joints has encountered the problem of leaking of the radioactive material throughout the lymph system. Particularly, the inventive delivery system is advantageous because of the large colloid particles, which with the heavy alpha particles and short half life, represent an improvement in the art.
A problem inherent in the use of alpha emitters is the delivery system. Previous attempts to attach alpha emitters to colloids have resulted in alpha emitters which are uniformly distributed through the colloid material. Because of relatively the short distances in which alpha emitters are effective, distribution of alpha emitting radionuclides throughout a colloid results in a very low dose of radioactivity being delivered to the affected area.
We have found that by plating the radioactive nuclide onto the outer surfaces of the colloid vastly improved results have been obtained.